Conventional pre-cast concrete stairs exhibit a number of disadvantages. Very often, such stairs are constructed in a form or mold that has a step-shaped bottom surface for defining the steps and an open upper end into which the concrete is poured. This form creates a stair that has a heavy flat slab along its bottom surface. Such a stair requires unnecessarily large amounts of concrete and is quite heavy. It requires a large crane to lift the stair into place. It is challenging to workers to place the heavy stair into the stairwell. Transportation of such stairs to the construction site is also expensive because of the limited number of stairs that can be transported on one truck. The landings or other support structures for holding these pre-cast stairs in position also have to be made stronger because of the weight of the stairs. This requires more concrete or other type of reinforcement material to support the stairs than is desirable.
One of the most common uses of concrete stairs is in the stairwells of large buildings to provide a fire escape. Building owners want to keep these stairs as narrow as possible to limit the size of the stairwell, which is nonproductive space. This is difficult because of the requirement that the stairs have rails.
Because of different building requirements and designs, stairs of different step widths are frequently required to be cast. The present forms for pre-casting concrete stairs cannot be adjusted to match varying widths of the stairs. A completely new form is required for each variation in stair width, which adds to the cost of casting stairs.
Concrete stairs can be cast in several sections and then put together at the building site. However, this approach suffers from the disadvantage of being highly labor intensive.